People use a variety of approaches to attain and maintain physical fitness. Physical fitness may include strength, flexibility, cardiovascular endurance, speed, balance, coordination, stamina, or other attributes (e.g., ability to perform specific tasks such as jumping or throwing a football). Many aspects of physical fitness can be realized by performing exercises that do not require special equipment, e.g., jogging, or push-ups. However, various exercise tools have been developed to enable individuals to achieve their physical fitness goals efficiently and consistently.
Physical training equipment is available in a variety of forms. From simple weight sets and exercise balls to sophisticated exercise machines typically only found in fitness centers, training tools share a common purpose: to augment the training capabilities of the human body alone. Undeniably, individuals must themselves exert sheer effort in order to achieve their fitness goals, but the tools they use may make the training process more efficient.
Conventional free weights, such as barbells and dumbbells, are renowned for their simplicity and versatility. One can perform many different free weight exercises to target various parts of the body by using gravity to counter muscular contractions. Some devices (e.g., bench racks and Smith machines) use weights in constrained manners (e.g., by constraining a range of motion). Other devices use a combination of weight stacks, rods, pulleys, and other mechanical means to provide gravity-based resistance for specific exercises. Yet other devices (e.g., rowing machines) use other means of resistance, such as hydraulic (shocks-based), water-based, air-based, or magnetic resistance.
These devices have several disadvantages. Free weights and machines are cumbersome. A set of fixed dumbbells, spanning a range of weights that might reasonably be needed to target various parts of the body, takes up a considerable amount of space. Adjustable barbells or dumbbells, which allow the addition or removal of weight plates, solve this problem but require time to make the adjustments. Training machines are typically large and target only a limited range of body parts. Individuals typically find it unaffordable to buy enough machines to target the entire body. Even machines that have been designed to provide a full-body workout while occupying a minimal footprint, e.g., certain machines by Bowflex®, suffer from another drawback shared by all of the foregoing devices: lack of portability. Additionally, many of the foregoing devices are not suitable for all people (e.g., children) to use.